A Review on Quality Preservation and Energy Efficiency in Refractance Window Drying
RW dryer can produce high-quality products with heat sensitive vitamins, phytochemicals content, color and antioxidant activity comparable to those of the freeze-dried products. The objective of this work is to present the recent trends in refractance window drying of foods. Detailed descriptions about typical dryer components and the mechanisms of heat and mass transfer during the drying process are presented. This review also includes an exhaustive summary on changes in Refractance Window Dryer product quality during RW™ drying of foods as compared to other drying methods such as tray, spray and freeze drying, based on available published works till date. In comparison with several conventional drying approaches, RW™ drying is known to offer superior quality powders and flakes at relatively lower operation costs and time requirements. To give a complete understanding on the topic, aspects of energy requirements and thermal efficiency calculations are also presented.
This study clearly showed that the drying technique used in the preparation of protein isolates can affect their functional properties. RW™ drying has shown to be a promising drying technology, mainly in time reduction as compared with conventional dehydration methods. Drying process of mango was carried out using RW drying, freeze drying, drum drying, and spray drying. Results showed that the color of RW-dried mango powder and reconstituted mango puree were comparable to the freeze dried products, but were significantly different from drum dried , and spray dried counterparts.
Basically, these are gas-solid contact operations working on gradients in water vapour pressures. Refractance Window is a relatively new drying technique for producing dried powders, slices or leathers from fruits and vegetables. In the present study, the effect of temperature (70, 80 and 90 °C) and thickness of puree on drying characteristics, mass transfer and quality attributes of RW dried banana puree were investigated. Results showed that drying at 90 °C reduced drying time (~61–64%) and energy consumption (~30–44%), as compared to drying at a lower temperature (70 °C) for both the thickness.
Evaluation of the mechanical damage on wheat starch granules by SEM, ESEM, AFM and texture image analysis. Meirelles, A. J. Development of a new refining process to maintain carotenes in edible palm oil. Water activity of fresh bee pollen and mixtures of bee pollen-honey of different botanical origin. & Kapur, P. Classification of tea grains based upon image texture feature analysis under different illumination conditions. Impact of powder particle structure on the oxidation stability and color of encapsulated crystalline and emulsified carotenoids in carrot concentrate powders. Effect of different drying procedures on the bioactive polysaccharide acemannan from Aloe vera .
Bodart, M., de Peñaranda, R., Deneyer, A. & Flamant, G. Photometry and colorimetry characterisation of materials in daylighting evaluation tools. Effect of different drying procedures on physicochemical properties and flow behavior of Aloe vera gel.
Drying of walnut kernels was done at different temperatures i.e., 50, 60, 70, 80 and 90 °C for 170 min, 150, 130, 120 and 110 min, respectively. Refractance window-dried walnut kernels were then compared with sun-dried walnuts that were dried under the sun for 5 days. The average drying temperature under the sun was between 23 and 25 °C, and the drying time was 9.4–9.8 h. Each day sample was kept under sunlight and collected back during sunset. The drying time for each experiment was kept based on preliminary experiments. High sugar content of fruits and vegetables causes some problems during drying of product in different drying systems.
Conductive hydro-drying also known as Refractance Window drying is a relatively new drying technology, which uses hot water to carry thermal energy to materials to be dehydrated. It has a high retention of heat sensitive quality parameters with better energy efficiency than freeze-drying as well as many other conventional drying methods. A new ultrasound and infrared assisted conductive hydro-dryer was developed to increase drying rate while reducing required hot water temperature and increasing the drying material thickness. The goal of this study was to evaluate the performance of the new dryer and to compare the performance of a pilot scale continuous UIACHD with a freeze-dryer and a cabinet dryer in drying apple slices.
On this basis, the Mylar™ film thickness could have been an RW™ drying process operational parameter, which could have affected to empirical parameters, but this behavior did not happen. The present study aimed to determine the effect of refractance window drying and compare it with sun drying for various physicochemical properties of walnut kernels. Physical properties such as moisture content, texture, color analysis, and water activity were analyzed and results were found to be better than sun drying.
The Mylar film takes the heat from the hot water (temperature below 99°C) at atmospheric pressure. The product slurry is spread over a transparent film evenly and the film permits the infrared energy at the speed of light to the product. The energy transfer due to conduction or radiation depends on the thermal resistance offered by the plastic film and the evaporation of moisture is by convection of air above the product. The air convection helps to lower the temperature during drying.
While swimming underwater, I looked up to see that the water’s surface acted like a mirror, only allowing me to see something floating on it but almost nothing else. I knew water was the best heat transfer medium in nature and wondered if perhaps water could be used to provide the energy needed to dry products. If so, it might do so more efficiently and without damaging the delicate and valuable nutrients in the food. Modeling of drying process in RW dryer and investigating the role of different parameters and heat transfer mechanisms in the process. Authors who have researched food area-related contact angles have based their work on studying the properties of materials’ surfaces in response to contact with liquid foodstuffs (i.e. interfacial interactions). Their usefulness as a mechanism for predicting interactions between liquids and solid surfaces (i.e. biofilms, membranes, heat interchange or packed food surfaces) has been studied by authors like Güleç et al.47.